The present invention relates to a vertical turbine pump and more particularly to such a pump which is resistant to clogging when handling fluids with entrained stringy materials and other solids.
Vertical turbine pumps are well known which operate in an upright position and employ a bowl assembly including a rotary impeller submerged in a body of liquid to be pumped. In these pumps, the impeller develops a diverging tangential flow of the liquid which passes through a bulbous diffusion zone and then through a discharge conduit and elbow.
When a vertical turbine pump is employed for pumping sewage and other liquids having considerable amounts of entrained stringy materials and other solids, clogging of the pump can be a problem. To avoid clogging, careful attention must be given to the size and shape of the passages in the impeller and in the downstream components of the pump. Generally, clog-resistant performance is realized by making the passages as large and as streamlined as possible.
A vertical turbine pump which can effectively handle liquids with entrained stringy materials and other solids is disclosed in U.S. Pat. No. 4,063,849 which issued to Modianos. The Modianos pump incorporates a bowl assembly having a fully shrouded two-vane impeller, a diffusion zone provided with two symmetrically disposed stationary vanes and a discharge column and elbow provided with an axially extending "splitter" vane.
When compared to vertical turbine pumps employing greater numbers of impeller and diffuser vanes, a vertical turbine pump having just two impeller vanes and two diffuser vanes exhibits limited hydraulic efficiency and generates significant pressure pulses which are manifested by relatively rough operation.
Vertical turbine pumps constructed according to known designs employ a pump bowl assembly having bowl bearings which are only accessible after completely disassembling the pump. Because of their location in the lower region of the pump, the bowl bearings are particularly vulnerable to wear and degradation when handling sewage and other corrosive and grit-laden liquids. Of the drive shaft bearings employed in a vertical turbine pump, the bowl bearings are usually the first to require servicing. In known vertical turbine pumps, the disassembly of the pump which is required in order to access the bowl bearings makes servicing of the bearings in the field a difficult prospect.